Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752262AbdGPODm (ORCPT ); Sun, 16 Jul 2017 10:03:42 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:43292 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751856AbdGPN6E (ORCPT ); Sun, 16 Jul 2017 09:58:04 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Josh Poimboeuf" , "Rafael J. Wysocki" , "Paul Menzel" , "Steven Rostedt (VMware)" Date: Sun, 16 Jul 2017 14:56:46 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 098/178] ACPI: Fix incompatibility with mcount-based function graph tracing In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1980 Lines: 53 3.16.46-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Josh Poimboeuf commit 61b79e16c68d703dde58c25d3935d67210b7d71b upstream. Paul Menzel reported a warning: WARNING: CPU: 0 PID: 774 at /build/linux-ROBWaj/linux-4.9.13/kernel/trace/trace_functions_graph.c:233 ftrace_return_to_handler+0x1aa/0x1e0 Bad frame pointer: expected f6919d98, received f6919db0 from func acpi_pm_device_sleep_wake return to c43b6f9d The warning means that function graph tracing is broken for the acpi_pm_device_sleep_wake() function. That's because the ACPI Makefile unconditionally sets the '-Os' gcc flag to optimize for size. That's an issue because mcount-based function graph tracing is incompatible with '-Os' on x86, thanks to the following gcc bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42109 I have another patch pending which will ensure that mcount-based function graph tracing is never used with CONFIG_CC_OPTIMIZE_FOR_SIZE on x86. But this patch is needed in addition to that one because the ACPI Makefile overrides that config option for no apparent reason. It has had this flag since the beginning of git history, and there's no related comment, so I don't know why it's there. As far as I can tell, there's no reason for it to be there. The appropriate behavior is for it to honor CONFIG_CC_OPTIMIZE_FOR_{SIZE,PERFORMANCE} like the rest of the kernel. Reported-by: Paul Menzel Signed-off-by: Josh Poimboeuf Acked-by: Steven Rostedt (VMware) Signed-off-by: Rafael J. Wysocki Signed-off-by: Ben Hutchings --- drivers/acpi/Makefile | 1 - 1 file changed, 1 deletion(-) --- a/drivers/acpi/Makefile +++ b/drivers/acpi/Makefile @@ -2,7 +2,6 @@ # Makefile for the Linux ACPI interpreter # -ccflags-y := -Os ccflags-$(CONFIG_ACPI_DEBUG) += -DACPI_DEBUG_OUTPUT #